Marine Chemistry最新文献

{"title":"Resilience of pH to seasonal change in a large subtropical lagoonal estuary","authors":"Paco Quintana ,&nbsp;Eunice Machado ,&nbsp;Rodrigo Kerr","doi":"10.1016/j.marchem.2025.104577","DOIUrl":"10.1016/j.marchem.2025.104577","url":null,"abstract":"<div><div>Coastal ecosystems exhibit a wide range of pH trends, from −0<em>.</em>023 to 0<em>.</em>023 pH units <em>yr</em>⁻¹, making them particularly susceptible to acidification or basification. These variations are primarily driven by ecosystem metabolism and the influence of oceanic and riverine endmembers, as observed in the subtropical system of the Patos Lagoon Estuary (PLE, southern Brazil), where biogeochemical variability is largely governed by mixing of water masses with different properties. This study provides the first quantification of the seasonal variability of pH buffering capacity in the inner and outer zones of PLE. From May 2017 to September 2023, we assessed temporal variability using multiple approaches: (i) carbonate system parameters, (ii) sensitivity factors, (iii) buffering capacity of pH to fractional change of dissolved inorganic carbon (<em>β</em>DIC), (iv) metabolic effects on pH, and (v) environmental drivers of pH. The results revealed a distinct seasonal pH pattern, especially between summer with winter and spring, with consistently higher values at the outer station compared to the inner station, though spatial differences were not statistically significant. In winter and particularly in early spring, calcium carbonate (<em>CaCO</em>₃) dissolution prevailed due to riverine input characterized by low buffering capacity. Along the salinity gradient, pH exhibited a pronounced difference, particularly between low and high salinity conditions. However, the persistent negative deviation of the metabolic effect on pH throughout the year and in salinity ranges, even under seawater conditions, supports the characterization of this coastal ecosystem as a net <em>CO</em>₂ source, with especially high variability at mid-salinity conditions. Although the salinity gradient was comparable between stations, they exhibited differences in the magnitude of pH sensitivity to seasonal biogeochemical changes. These findings indicate that PLE functions as a system with moderate to low buffering capacity, with the outer zone showing greater resilience to pH fluctuations.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104577"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145622899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new sub-routine for the molecular component of the mixed-kinetics dissolution model of CaCO3 in seawater-like solutions","authors":"Victor W. Truesdale ,&nbsp;Jim Greenwood ,&nbsp;Tim Southern","doi":"10.1016/j.marchem.2025.104599","DOIUrl":"10.1016/j.marchem.2025.104599","url":null,"abstract":"<div><div>As a prelude to further understanding the dissolution kinetics of CaCO₃ in the oceanic water-column, the principles of Chemical Kinetics are applied generally to what recently was defined as the <em>solution-oriented approach</em> to CaCO₃ dissolution kinetics. The ultimate objective of the study is to probe what is known commonly as, the ‘mixed-kinetics model’ for dissolution; a sequence of molecular and diffusion reactions derived, historically, from the use of the spinning-disc reactor. As a first step, the paper shows how carbonate chemistry can be introduced into the molecular component, to generate the ions that subsequently diffuse across the hydrodynamic boundary layer surrounding the solid, into the bulk solution. The intention is to discover how control of the whole reaction shifts between molecular and diffusion components with change in stirring conditions, as that condition is a significant barrier to linking laboratory and field studies. In the interim, however, the study presents four archetypal, [Ca²⁺] versus time plots (geometric templates) that cover reactors either open or closed to CO₂, and in which pH is either fixed or variable. These plots provide a better alternative to the more common one of rate versus reaction extent, Ω, favoured in oceanography, but which has proved to be unsatisfactory. In turn, these new templates are compared with existing standard kinetics curves, for example, one from the analytic solution for a non-hydrolysing AB-salt, e.g., gypsum.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104599"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence for weathering of silicate minerals in ocean columns as the primary source of oceanic alkalinity","authors":"Tasuku Akagi,&nbsp;Hirotaka Nishino","doi":"10.1016/j.marchem.2025.104603","DOIUrl":"10.1016/j.marchem.2025.104603","url":null,"abstract":"<div><div>Based on the correlated increase of alkalinity (At) with that of silicic acid concentration [Si] in the Atlantic Ocean, the contemporaneous dissolution of carbonates and opal in the water column has been proposed as the mechanism for alkalinity production. We revisited existing datasets to examine, in greater detail, the relationship between oceanic At, [Si], total dissolved inorganic carbon (TIC) and its carbon stable isotope ratios (δ¹³C), to examine which of the two possible alkalinity sources, carbonate dissolution or silicate mineral weathering, is the most probable source of alkalinity.</div><div>We invariably find that At and [Si] are correlated and the slope ΔAt/ΔSi is almost identical for the intermediate water (2 &lt; potential temperature, <em>θ</em> &lt; 8 °C) of Atlantic, Indian and Pacific oceans. The At and [Si] correlation is difficult to explain by carbonate + opal dissolution, since the carbonate and biogenic opal production rates differ widely among the ocean basins.</div><div>We investigated the carbon sources from δ¹³C measurement of total dissolved inorganic carbon (TIC) in the intermediate water (2 &lt; <em>θ</em> &lt; 8 °C) and in the deeper water (<em>θ</em> &lt; 2 °C), separately. Waters characterized by the same pH are used in the investigation, since the δ¹³C of TIC generated during carbonate dissolution is constrained. In the intermediate water, the resulting data do not support the notion of carbonate dissolution as the alkalinity source, whereas in the deeper water both carbonate dissolution and silicate mineral weathering are shown as the producers of alkalinity. Carbonate dissolution only acts to relocate surface alkalinity to the deep water. We infer that dissolution of terrigenous silicate minerals within the oceans (a process we refer to as “ocean silicate weathering”) is the primary source of alkalinity in the oceans. This interpretation also explains the linear relationship between At and [Si] in the water.</div><div>Our findings do not contradict the conventional understanding of oceanic silicon cycles, if biogenic opal contains weatherable siliceous material. We previously showed that such matter is present in diatom frustules. Its uptake by fauna in deep water may provide a compelling explanation for the coupling of increases in [Si] and At. It is shown that ocean silicate weathering is a key to understanding the mechanism of CO₂ absorption by the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104603"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Riverine turbidity overrides nutrient enrichment in regulating coastal volatile sulfur compounds cycling","authors":"Qian-Yao Ma ,&nbsp;Jun-Qi Yang ,&nbsp;Meng-Yan Yu ,&nbsp;Jiao-jiao Pang ,&nbsp;Gui-Peng Yang","doi":"10.1016/j.marchem.2025.104586","DOIUrl":"10.1016/j.marchem.2025.104586","url":null,"abstract":"<div><div>Volatile sulfur compounds (VSCs), including dimethyl sulfide (DMS), carbonyl sulfide (COS), and carbon disulfide (CS₂), play key roles in atmospheric chemistry and climate regulation. Riverine discharge supplies nutrients and chromophoric dissolved organic matter (CDOM) that can potentially stimulate the production of VSCs. Yet, field observations in many estuarine regions have revealed surprisingly low VSCs levels, implying that riverine enrichment alone cannot explain their variability. In this study, concentrations of DMS, COS, and CS₂ were quantified in surface waters, vertical profiles, and the overlying atmosphere of the Bohai and Yellow Seas during spring and summer 2024. Average surface concentrations of DMS, COS, and CS₂ were 6.3, 0.11, and 0.09 nmol L⁻¹ in spring, increasing to 9.7, 0.35, and 0.19 nmol L⁻¹ in summer. DMS showed strong positive correlation with chlorophyll-<em>a</em>, while COS correlated with CDOM. Riverine inputs of nutrients and CDOM from the Yellow River enhanced VSCs production, although elevated turbidity limited light availability and thus suppressed biological and photochemical pathways. Atmospheric mixing ratios in spring averaged 61.1, 408.7, and 105.5 pptv for DMS, COS, and CS₂, respectively. The estimated sea-to-air flux demonstrated that DMS was the dominant contributor to atmospheric sulfur in the study region, with fluxes of 5.4 μmol m⁻² d⁻¹ in spring and increasing to 15.0 μmol m⁻² d⁻¹ in summer. These results highlight the vital role of riverine discharge in modulating both nutrient supply and turbidity, thereby regulating the biological and photochemical pathways that control VSCs production and their subsequent sea-to-air emissions in coastal waters.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104586"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145614312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variations in lignin content deposited in the Congo fan and its potential for oxidative degradation","authors":"Louis C. Bondurant ,&nbsp;Megan L. Baker ,&nbsp;Sophie Hage ,&nbsp;Peter J. Talling ,&nbsp;Patrick G. Hatcher","doi":"10.1016/j.marchem.2025.104569","DOIUrl":"10.1016/j.marchem.2025.104569","url":null,"abstract":"<div><div>The deposition of terrigenous organic carbon (tOC) in offshore deep-marine settings has traditionally been viewed as inconsequential for organic carbon burial. However, it has been shown that deep-sea sediment flows, turbidity currents, can contribute significantly to the burial of tOC. Elemental, isotopic, and molecular data were obtained on sediment samples from three areas within and adjacent to the Congo Deep-Sea Fan. The elemental, organic geochemical, and isotopic data agree well with previous studies from the Congo Fan, which show that terrigenous organic matter from the Congo River extends seaward in the axis of the submarine canyon to abyssal depths. Using advanced solid-state ¹³C NMR and TMAH thermochemolysis data we verify that a significant amount of lignin is exported to the canyon (∼14 % wt. lignin) and the distal lobe (∼16 % wt. lignin) sediments. The basin plain contains no detectable lignin but does show the presence of terrigenous long-chain fatty acids having an even carbon number predominance. Following a laboratory oxidation experiment on sediments from the distal lobe for 6 d there was an organic carbon mass loss of 59.8 % and the solid-state ¹³C NMR spectrum shows a major reduction in peaks associated with carbohydrate-like and lignin molecules and a relative increase in aliphatic molecules. This shows that terrigenous lignin molecules can be remineralized to CO₂ and/or altered to structures that no longer resemble that of lignin through oxidative degradation processes. This would have a potentially significant implication on what is traditionally viewed as autochthonous marine organic matter.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104569"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MNPs in marine environment: Sources, distribution, trophic transfer, toxicity, fate and the remediating role of epiplastic syntrophic microbial consortia (Biofilms)","authors":"Smarto Basak ,&nbsp;Amit Kumar Dixit ,&nbsp;Ranjit Kumar Dey ,&nbsp;Gajji Babu","doi":"10.1016/j.marchem.2025.104553","DOIUrl":"10.1016/j.marchem.2025.104553","url":null,"abstract":"<div><div>This review focuses on plastic pollution, which has emerged as an urgent environmental issue with microplastics (MiPs) and nanoplastics (NaPs) being widespread contaminants in marine ecosystem. These particles pose serious ecological and public health risks due to their ability to bioaccumulate and vertically transfer through the food chain rapidly. Ingestion of MiPs and NaPs (MNPs) causes harmful physiological and reproductive effects, threatening the stability and integrity of marine food chains. This review summarizes the sources, distribution, trophic transfer, toxicity and fate of MNPs involving the marine ecosystem. Microbial communities have displayed potential as remediating agent for MNPs; though the processes involved in NaP degradation remain poorly understood, highlighting the need for further research. The distinctive properties of NaPs complicate their interactions with microbial communities, pointing to the necessity for focused studies on their biodegradation pathways. This review advocates for a holistic strategy that employs epiplastic syntrophic microbial consortia (Biofilm) as bioremediating agents, as their interactions may enhance breakdown of MNPs in marine setting. Future research should aim to clarify the relationships between microbial consortia and NaPs, identifying ideal conditions that foster microbial growth and activity on these NaPs. This review will be helpful for innovating effective management strategies to reduce the impacts of these established pollutants; ultimately, increasing our understanding of MNPs in marine environment, which is critical for shaping policies that safeguards the future of marine ecosystem and public health. Tackling plastic pollution requires a collaborative approach across all scientific fields, emphasizing the gravity of this global challenge.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104553"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mapping of dissolved black carbon in the Atlantic Ocean","authors":"Nina Davtian ,&nbsp;Nuria Penalva ,&nbsp;Oriol Teruel ,&nbsp;Pau Comes ,&nbsp;Antoni Rosell-Melé ,&nbsp;Joan Villanueva","doi":"10.1016/j.marchem.2025.104568","DOIUrl":"10.1016/j.marchem.2025.104568","url":null,"abstract":"<div><div>Oceanic dissolved black carbon (DBC) is the subject of a conundrum between the dominant riverine inputs in terms of mass flux and its stable and radiogenic carbon isotope composition inconsistent with a predominant riverine origin. Here, we analyzed seawater samples within specific and contrasting water masses along several latitudinal and longitudinal transects across the Atlantic Ocean to quantify DBC and map its latitudinal and water depth changes in this ocean. After comparing latitudinal changes in surface water DBC properties with those in atmospheric pyrogenic carbon inputs from seasonal, massive grass burning events in the African Savanna, we could not demonstrate the significance of atmospheric deposition as a non-riverine source of DBC in the Atlantic Ocean, likely due to the balance by DBC photo-bleaching. We found constant DBC concentrations and increasing trends in the condensation degree of DBC (i.e., B6CA:B5CA molar ratio) from surface to deep Atlantic waters and from the South Atlantic to the North Atlantic within individual shallow to deep water masses. Overall, our mapping of DBC in the Atlantic Ocean highlights the need to explore the following alternative hypotheses in the future to better understand the cycling of oceanic DBC: 1) enhanced regional atmospheric BC deposition from African savanna grassland fires impact particulate rather than dissolved BC in the Atlantic Ocean, 2) oceanic DBC has a predominantly non-pyrogenic origin, and 3) exports of terrigenous DBC across the Atlantic Ocean accompany those of terrigenous humic-like compounds from the North Atlantic via meridional circulation.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104568"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relationships between chemical composition of Arctic FeMn formations and their sorption properties for 137Cs and 90Sr radionuclides","authors":"Svetlana Bratskaya ,&nbsp;Andrey Egorin ,&nbsp;Denis Balatskiy ,&nbsp;Marina Palamarchuk ,&nbsp;Natalia Polyakova ,&nbsp;Alexander Ulyantsev","doi":"10.1016/j.marchem.2025.104582","DOIUrl":"10.1016/j.marchem.2025.104582","url":null,"abstract":"<div><div>Shallow-water Fe<img>Mn formations in Arctic are usually not considered as a valuable mineral resource due to sub-economic contents of rare earth and critical metals. However, fast growth rate and unique chemical composition make them interesting candidates for application in environment protection and remediation. Here we have investigated the potential of the Chaun Bay (East Siberian Sea) Fe<img>Mn formations for application as selective sorbents for ¹³⁷Cs and ⁹⁰Sr. Fe<img>Mn formations collected at three stations located inside and nearby submarine groundwater discharge demonstrated highly variable chemical compositions with Fe/Mn ratios (0.058–0.71) and element contents up to 26.65 % (Fe), 17.79 % (Mn), 4.40 % (P), 6.34 % (Al), 15.52 % (Si). Sr contents varied from 880 to 2560 ppm. Akaganeite (β-FeOOH) was identified as the main Fe phase in crusts, while nodules were composed by lepidocrocite (γ-FeOOH) and/or feroxyhite (δ-FeOOH). Sorption properties of Fe<img>Mn formations toward ¹³⁷Cs and ⁹⁰Sr were investigated from low salinity solutions and seawater. The sorption capacity and distribution coefficients <em>(K</em>_d<em>)</em> for ¹³⁷Cs correlated with aluminosilicates contents, while all phases (Fe and Mn oxyhydroxides, phosphates, and silicates) contributed to the ⁹⁰Sr uptake. Fe<img>Mn formations with high P and Mn contents demonstrated an ultimately high selectivity toward ⁹⁰Sr in seawater with K_d up to 517 mL/g for Mn-rich sample that is comparable or better than the selectivity of the most known synthetic sorbents. The results obtained not only confirm the possibility of Fe<img>Mn nodules application for radioactive waste treatment but open up prospects for the nature-inspired design of the composite sorption materials.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104582"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145568513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acid-leachability of metals from suspended particles in the Pacific Ocean","authors":"Yoshiki Sohrin ,&nbsp;Linjie Zheng ,&nbsp;Cheuk-Yin Chan ,&nbsp;Yuzuru Nakaguchi ,&nbsp;Shotaro Takano ,&nbsp;Rumi Sohrin ,&nbsp;Wen-Hsuan Liao ,&nbsp;Tung-Yuan Ho","doi":"10.1016/j.marchem.2025.104571","DOIUrl":"10.1016/j.marchem.2025.104571","url":null,"abstract":"<div><div>Suspended particles are major carriers of trace metals in seawater, while the cycling mechanisms of particulate trace metals remain largely unclear owing to analytical challenges. In this study, we focused on the acid-leachability of particulate trace metals collected from the Pacific Ocean and investigated their compositional features by measuring the total dissolvable metal (tdM) and dissolved metal (dM) concentrations in unfiltered and filtered seawater samples, respectively. We defined the difference between total dissolvable and dissolved metals as the particulate metal (pM). We investigated the pM time course in acidified bottom waters (pH 1.9) over approximately two years. pM increased in two stages and reached equilibrium within a few years. In the field study, we stored acidified seawater samples at least two years before analysis. We compared pM with total particulate metal (tpM) concentrations in the same samples collected from 11 stations in the subarctic Pacific. The tpM concentrations were determined by particle filtration followed by total digestion using strong acids, including HF. The results indicate that pAl and pFe are nearly equivalent to tpAl and tpFe, respectively. Many metals in the suspended particles, including clay minerals, are highly acid-leachable during long-time storage. By compiling our pM data observed in the Pacific Ocean and its marginal seas (approximately 1500 samples), we found that the average pM/dM ratio across the Pacific is 9 for Al and 4 for Fe. Although pAl and pFe exhibit strong linear correlations, their concentrations and regression slopes are spatially variable, reflecting differences in sources and fluxes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104571"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Groundwater modulates nutrient dynamics in a freshened saltmarsh tidal creek","authors":"Jianan Liu ,&nbsp;Xueqing Yu ,&nbsp;Tong Peng ,&nbsp;Xinyi Lin ,&nbsp;Jinzhou Du","doi":"10.1016/j.marchem.2025.104566","DOIUrl":"10.1016/j.marchem.2025.104566","url":null,"abstract":"<div><div>Saltmarsh tidal creeks play a critical role in coastal nutrient cycling, yet submarine groundwater discharge (SGD), as a key driver, remains poorly understood. Research on SGD-derived outwelling of multiple nutrient species is notably scarce in low-salinity estuarine saltmarshes influenced by large rivers. Utilizing long-lived radium isotopes (²²⁶Ra and ²²⁸Ra) combined with high-frequency monitoring encompassing the most comprehensive species of dissolved nutrient to date during both spring and neap tides, we quantified SGD fluxes and their contribution to nutrient outwelling in a low-salinity saltmarsh tidal creek system of the Yangtze River Estuary. Results showed that driven by tidal pumping, SGD flux during spring tides (12 ± 5.9 cm d⁻¹) was significantly greater than during neap tides (0.77 ± 0.42 cm d⁻¹), along with corresponding differences in nutrient transport fluxes. SGD served as a source of dissolved inorganic nitrogen (DIN) and dissolved silicate (DSi) to the tidal creek system. Specifically, NH₄-N contributed approximately 93 % of the outwelling flux, while SGD-derived DSi accounted for 31–36 % of the DSi outwelling. Conversely, SGD functioned as a sink for dissolved phosphorus (inorganic + organic), capable of removing phosphorus in the tidal creek waters. More importantly, due to nitrogen input via SGD and its retention of phosphorus, both groundwater and ebbing tidal creek waters exhibited nitrogen-to‑phosphorus (N/P) ratios significantly exceeding the Redfield ratio. Although the saltmarshes partially mitigated the elevated N/P ratio during the outwelling process, the imbalanced N/P ratio in SGD-driven outwelling still poses risks of inducing coastal eutrophication and harmful algal blooms. This study unveils the crucial regulatory role of SGD in nutrient dynamics within low-salinity saltmarshes, emphasizing the necessity to incorporate groundwater-surface water interactions into coastal nutrient management and ecological conservation.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104566"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}